Gain control regulator



oct. 27, 1935.

H. BROADWELL GAIN CONTROL REGULATOR F1155 sept. 11, 1955 2 Sheets-Sheetl ATTORNEY Oct. 27, 1936.

H. BROADWELL GAIN CONTROL REGULATOR Filed Sept. ll, 1955 2 Sheets-Sheet2 4/42 4o I9 34 /1 a3 2 2a a 29 a0 75 /6 3/ 1 38 /NVENTOR H. BROADWELLnel? i? AT TOR/VEV Patented Oct. 237, 1936 UNITED STATES PATENT QFFICEGAIN CONTROL REGULATOR Howard Broadwell, Ridgewood, N. J., assignor toBell Telephone Laboratories,

Incorporated,

2 Claims.

This invention relates to arrangements for maintaining constant thetransmission level of a transmission circuit, and more particularly to amotor driven regulator for such systems, and its object is to provide adevice of this character which will be simple, cheap to manufacture,easy to assemble, and efficient in operation.

The device of this invention is designed for use in a system such asdisclosed in Patent No. 1,918,390 to E. I. Green.

A feature of this invention consists in the provision of a series ofresistances mounted in molded arcuate mountings, the terminals of whichare adapted to be engaged by radially extending contact springs pressedinto engagement with the terminals by an operating arm, the engagedpressure of which is adjustable so as to ensure proper closure of thecontacts without damage to the unit. Preferably the contacting fingersare of a short heavy type to prevent side sway and are provided withmeans engageable with the molded arcuate mounting, if necessary, toprevent overstraining when depressed by the operating roller arm. Theroller arm is mounted on a V-shaped spring secured to a saddle or framewhich straddles a shaft and is held loosely thereon by a shoulder pinretained in place by a spring clip. The saddle is made slightly narrowerthan the shaft and is sprung into place to eliminate play due tovariations. An adjustable screw is mounted in the top of the saddle, andits end rests against the shaft when the roll-er arm is under tension.This arrangement of pivot pin and screw provides the equivalent of athree point support which, when the roller is under tensionautomatically produces a rigid arm free from shake even when a largeamount of initial play is present in the parts, and by turning thisscrew with an ordinary screw drive inserted down between the units thesaddle is rotated slightly on its pivot pin, thus increasing ordecreasing the pressure of the roller against the finger springsbeneath. This arrangement eliminates bending of the spring fortensioning purposes, which is dinicult and especially impractical whenthe units are mounted on close centers as in this type of apparatus.

Another feature consists in the provision of means for permitting handrotation of the shaft without disturbing the position of the roller armsof the other resistance units on the same frame for testing purposes.

Other novel features and advantages of the invention will appear fromthe following description and by the claims appended thereto, referencebeing had to the accompanying drawings in which Fig. 1 is a frontassembly View of a group of resistance units showing a number ofoperating parts with portions cut away;

Fig. 2 is a cross-sectional view taken on line 2 2 of Fig. 1;

Fig. 3 is a cross-sectional view of a resistance unit taken on line 3 3of Fig. 2;

Fig. 4 is a front View of a clutch mechanism for operatively connectingand disconnecting the driven shafts from the driving shaft, the clutchbeing shown in disengaged position; and

Fig. 5 is a front elevation View showing the driving co-nnections of aplurality of groups of resistance units in assembled relation on anupright support.

As shown in the drawings, I0 is a rectangularly shaped casing portionhaving integrally formed therewith a number of bosses II shown in Fig. 2for mounting the angle bars I2 and I3 which are held securely thereon bya number of screws SC. The bars I2 and I3 are provided with a pluralityof cooperating notches III and I5 for receiving registering parallelportions I8 oi a number of semi-circular shaped plates P for readilylocating them in equal spaced and in right-angled relation to the shaftas shown in Fig. 1, and also preventing snagging which would result inan improper registration of the two contact springs with theirassociated posts 62 when mounting the resistance unit in place. 'Iheseplates are held securely on the angle bars I2 and I3 by resp-ective setsof screws lil-20, 2I-22 and 23-24, while the casing I0 and the anglebars I2'and I3 may be made of any desired length for receiving anynumber of plates P.

On each plate P is securely mounted as by similar screws 25, 26 and 2'Ian arcuate channel shaped mounting 28 of insulating material formounting a semi-circular row of contact members, such as CM, eachprovided with a terminal portion 29 shown in Fig. 3 connecting with aplurality of resistance devices 3D.

On plates P and in concentric relation with the arcuated mounting 28there is secured a block 3I of insulating material shown in Figs. 2 and3 provided for mounting two semi-circular rows of superposed contactsprings 32 and 33 formed in a comb-like punching and extending radiallyin engageable relation with the contact points CM on the arcuatedmounting 28 but normally tensioned for abutment with the underside of aplate 34 held on the insulating mounting 28 by the screws 25, 26 and 21,these contact springs being fork shaped at their free ends and eachprong provided with a contact point for engaging a CFI common terminalCM. There are four comb-like punchings per unit. The fingers of eachuppe1 disposed punching 33 are offset a denite amount to shorten themslightly compared with those below to compensate for their higherposition in the pileup, thus permitting the use of one finger stampingdie in place of two for the entire unit.

Casing I0 is provided at each end with bearing portions 35 and 36provided for journaling shaft 31 in concentric relation with theinsulating mounting 28 and on this shaft are pivotally mounted similarbrackets 38 for movement at right angles with respect to the turningmovement of shaft 31, through the adjustment of screws 39, shown inFigs. 2 and 3, and on each of these brackets is mounted a V-shapedspring arm 40 provided at its free end portion with a stud 4l formounting a roller 42 for successively engaging the springs 32 and 33with the contact points CM upon the rotation of shaft 31, correctContact pressure being automatically determined by setting the screws 39to exert a predetermined pressure value on the roller arms 40. Twofinger springs will be depressed simultaneously when the roller moves toa position between adjacent springs, thus providing a passing Contactcondition. The dimensions of the contact springs and roller arm springare suitably worked out so that even under extreme conditions ofcommercial variation in thickness of the roller arm spring, suitableContact pressure, even with two contact springs depressed, will beprovided without overstrain of the roller spring or excessive rollertension, when the roller pressure is adjusted to its predeterminedvalue. The springs 32, 33 are made short and relatively heavy withleaders 15 (Fig. 2) extending downward at an angle to ensure properengagement of the spring by the roller. Projections are provided on themolded mounting under the roller engaging portions of the contactsprings which limit, if necessary, the motion of the springs to preventoverstraining. A clutch arm 43 having at its free end portion twolaterally extending prongs Pl and P2 is securely mounted on one end ofeach shaft 31 and extends radially therefrom for engaging with a springarm 44 carried by a bevel gear 45 loosely mounted on the extreme end ofshaft 31 and held against lateral movement thereon by a nut 46 engagingthe threaded portion 41 of this shaft, a scale 48 shown in Figs. 1 and 5being provided for indicating in conjunction with an index 49 theposition of the arms 40 with respect to their associated contacts CM.

The gears 45 of resistance groups X, XI and X2 shown in Fig. 5 areoperatively connected to a common driving shaft 50 through gears 5l andthis shaft is actuated by a motor M through a gear reduction mechanismwhich may take the form of a worm 52 on the armature shaft of the motorand a worm gear 53 secured at the end of driving shaft 50.

In a typical example of operation, the movement of shaft 50 through theoperation of the motor M under control of a regulating mechanism (notshown) is effective to rotate the shafts 31 of resistance groups X, Xland X2 for moving the spring arms 40 of each group successively on theirassociated rows of contact springs 32 and 33 for engaging the contactsCM and thereby cutting in and out of the circuits the resistance 35connected to the terminal portions 29 of contacts CM, the screw 39 beingadjusted as to force the arms 40 against the contacts 32 and 33 so as toobtain the proper pressure of the contact springs j resistance groupsunder the control of the motor M. Removal of any one of the supportingplates P from the casing portion I3 is effected by removing itsfastening screws {9 20 or 2l--22 as the case may be without the breakingof any soldered connections since electrical connection from theresistance is effected by springs B and 6I mounted on the parallelportions of plate P and engaging the terminals 62 and 63 secured tocasing portion I0, this casing having portions such as 64 and 65 forreceiving the screws 66 and 61 serving for securing the complementarycasing portions 63 as shown in the drawings in order to effectivelyprevent dust reaching the contacts and other operating parts of thedevice.

What is claimed is:

1. In a resistance device, a mounting plate having a pair of parallellydisposed arms, a casing, a pair of bars mounted in parallel relation insaid casing and having corresponding grooves for engaging the oppositeedges of said arms for readily locating said plate in adjusted relationon said bars, movable and stationary contacts mounted on said plate, arotatable shaft, and means carried by said shaft for successivelyoperating said movable contacts.

2. In a resistance device, a group of resistances, terminals therefor, aseries of radial contact springs adjacent thereto, a roller for engagingsaid springs with said terminals, a V-shaped spring mounting for saidroller, a saddle to which said spring is secured, a shaft on which saidsaddle is mounted and held rotatably thereon by a pivot pin passingthrough an opening on the shaft, and an adjusting screw passing throughthe saddle and engaging the shaft.

HOWARD BROADWELL.

Cil

